Monte Carlo simulations of copolymers at homopolymer interfaces: Interfacial structure as a function of the copolymer density

TL;DR

This study uses Monte Carlo simulations to analyze how adding AB diblock copolymers affects the interfacial structure between demixed homopolymer phases across various concentrations, revealing broadening profiles at higher concentrations.

Contribution

It provides a detailed simulation-based analysis of copolymer effects on homopolymer interfaces, introducing a novel block analysis method for profile calculation.

Findings

Profiles broaden with increased copolymer concentration

Results align well with self-consistent field calculations

Different regimes (mushroom, wet brush) characterized by concentration effects

Abstract

By means of extensive Monte Carlo simulations of the bond fluctuation model, we study the effect of adding AB diblock copolymers on the properties of an interface between demixed homopolymer phases. The parameters are chosen such that the homopolymers are strongly segregated, and the whole range of copolymer concentrations in the two phase coexistence region is scanned. We compare the ``mushroom'' regime, in which copolymers are diluted and do not interact with each other, with the ``wet brush'' regime, where copolymers overlap and stretch, but are still swollen by the homopolymers. A ``dry brush'' regime is never entered for our choice of chain lengths. ``Intrinsic'' profiles are calculated using a block analysis method introduced by us in earlier work. We discuss density profiles, orientational profiles and contact number profiles. In general, the features of the profiles are similar at all copolymer concentrations, however, the profiles in the concentrated regime are much broader than in the dilute regime. The results compare well with self-consistent field calculations.